Hyperinsulinemia-induced vascular smooth muscle cell (VSMC) migration and proliferation is mediated by converging mechanisms of mitochondrial dysfunction and oxidative stress

Abstract

Atherosclerosis is one of the major complications of diabetes and involves endothelial dysfunction, matrix alteration, and most importantly migration and proliferation of vascular smooth muscle cells (VSMCs). Although hyperglycemia and hyperinsulinemia are known to contribute to atherosclerosis, little is known about the specific cellular signaling pathways that mediate the detrimental hyperinsulinemic effects in VSMCs. Therefore, we investigated the cellular mechanisms of hyperinsulinemia-induced migration and proliferation of VSMCs. VSMCs were treated with insulin (100 nM) for 6 days and subjected to various physiological and molecular investigations. VSMCs subjected to hyperinsulinemia exhibited increased migration and proliferation, and this is paralleled by oxidative stress [increased NADPH oxidase activity, NADPH oxidase 1 mRNA expression, and reactive oxygen species (ROS) generation], alterations in mitochondrial physiology (membrane depolarization, decreased mitochondrial mass, and increased mitochondrial ROS), changes in mitochondrial biogenesis-related genes (mitofusin 1, mitofusin 2, dynamin-related protein 1, peroxisome proliferator-activated receptor gamma coactivator 1-alpha, peroxisome proliferator-activated receptor gamma coactivator 1-beta, nuclear respiratory factor 1, and uncoupling protein 2), and increased Akt phosphorylation. Diphenyleneiodonium, a known NADPH oxidase inhibitor significantly inhibited migration and proliferation of VSMCs and normalized all the above physiological and molecular perturbations. This study suggests a plausible crosstalk between mitochondrial dysfunction and oxidative stress under hyperinsulinemia and emphasizes counteracting mitochondrial dysfunction and oxidative stress as a novel therapeutic strategy for atherosclerosis.